High efficiency dehumidifiers and combine dehumidifying/air-conditioning systems

ABSTRACT

An air-conditioning system for conditioning air by removing heat and moisture from the air and transferring it to the environment, comprising: a dehumidifier ( 14 ) that produces dehumidified air and utilizes a liquid desiccant for drying; at least one non-desiccant fluid at a temperature lower than the temperature of the liquid desiccant; and at least one heat exchanger ( 20 ) in which the liquid desiccant is cooled by the at least one fluid.

RELATED APPLICATIONS

The present application is a U.S. national application of PCTApplication No. PCT/IL01/01207, filed on Dec. 27, 2001.

FIELD OF THE INVENTION

The present invention is related to the field of environmental controlsystems and more particularly, to the field of dehumidifiers, andsystems which combine dehumidification and air conditioning.

BACKGROUND OF THE INVENTION

There have been two general approaches to the design of systems thatcombine air conditioning and dehumidification. In one approach, the airis cooled down to the dew point for the desired final moisture content,in order to remove all undesired moisture. Because this dew point isgenerally below the desired final air temperature, the air at this dewpoint must then be heated, usually by mixing it with air that is alreadyin the room being air conditioned.

In the second approach, the air is dehumidified, before cooling it, byexposing it to a desiccant, which absorbs moisture from the air. If theabsorption of moisture by the desiccant takes place without any heatflow, i.e. at constant enthalpy, then the air will become hotter as itis dehumidified. The air must then be cooled even more than if it hadremained at the outside temperature, which also lowers the efficiency ofthe air conditioner.

For this reason, it is generally considered to be desirable to removeheat from the desiccant while it is absorbing moisture. In adehumidifier described in U.S. Pat. No. 6,018,954, a heat pump is usedto remove heat from the desiccant while it is absorbing moisture, and totransfer the heat to a regenerator where the desiccant gives offmoisture so that it can be used again.

In any dehumidifier using a desiccant, it is desirable to expose a largesurface area of desiccant to the incoming air, in order to maximize thethroughput of air that can be dehumidified. In the case of liquiddesiccant, a large surface area has been produced by spraying smalldroplets of desiccant through the air, and by dripping the desiccantonto a sponge. Because the desiccant quickly becomes saturated withmoisture if it has a large surface area, in all of these dehumidifiersthere is a reservoir of desiccant which does not have a large surfacearea. When the dehumidifier is operating, the desiccant is continuouslydrawn from the reservoir, a small quantity of the desiccant is exposedto the air in a form with a large surface area (droplets, or sponge, forexample) and it is then returned to the reservoir. Dehumidifiers using areservoir in this way are described in U.S. Pat. No. 6,018,954, and inPCT patent publications WO 99/26025 and WO 99/26026, the disclosures ofwhich are incorporated herein by reference. On a slower time scale, asthe absorbed moisture builds up in the reservoir, the desiccant in thedehumidifier reservoir is circulated into a regenerator, where themoisture is removed from the desiccant by heating it, and the desiccantis circulated back into the dehumidifier reservoir. Within theregenerator, desiccant is also drawn from a reservoir and a smallquantity is exposed to the air in a form with a large surface area, forexample droplets or a sponge, to speed up the rate at which the moistureis removed from the desiccant.

Modern room air conditioners generally use mechanical heat pumps to coolthe air, which requires a large power input. A more energy efficientmethod of cooling air, known since ancient times, is to use a fan toblow the air past evaporating water. This method consumes much lessenergy than a heat pump, because it makes use of the free energyinherent in ambient air at less than 100% humidity. By comparison withthis free energy, the energy consumed by the fan is trivial. Thedisadvantages of evaporative cooling are that the air that is cooled hasa higher moisture content than the ambient air, and the method doesn'twork well at high ambient humidity. Nevertheless, evaporative cooling isoften used to cool open environments, for example stockyards, where lowhumidity is not so important, ambient humidity is not too high, and lowpower consumption is important. Evaporation of water has also been usedto cool the refrigerant in heat pumps used in many cooling systems, and(as described in U.S. Pat. No. 6,018,954) to cool the refrigerant usedin a heat pump used for cooling the desiccant in a dehumidifier andheating the desiccant in the associated regenerator.

SUMMARY OF INVENTION

An aspect of some embodiments of the invention relates to dehumidifierswith a dehumidifying section, where liquid desiccant removes moisturefrom the air being dehumidified, and a regenerating section, wheremoisture is removed from liquid desiccant, generally by using heat toevaporate the moisture into the air, and the moist air is returned tothe outside environment. In these embodiments, in one or both of thesesections, one or more moving elements containing liquid desiccant areexposed to the air, and repeatedly dip into and out of a reservoir ofliquid desiccant, replacing the desiccant they are holding withdesiccant from the reservoir. In the case of the dehumidifying section,as the desiccant on the moving elements becomes saturated with moisture,it is replaced with fresh desiccant from the reservoir. In the case ofthe regenerating section, as the desiccant on the moving elements losesits moisture to the air, it is replaced by desiccant from the reservoirwhich still needs to have moisture removed from it.

Optionally, the elements comprise an absorbent material such felt orsponge attached to a surface. Alternatively, the elements comprise oneor more cups or other holders for the desiccant. Alternatively oradditionally, the desiccant sticks to a nonabsorbent surface of theelements due to its viscosity or surface tension.

Optionally, the elements are mounted on the blades of a propeller orwindmill, which is caused to turn by the incoming air current, and theblades dip in and out of the reservoir as the windmill turns. Thisdesign has the advantage that if the air streaming into the dehumidifierspeeds up or slows down, and the desiccant consequently gets saturatedmore quickly or less quickly, then the moisture laden desiccant isautomatically replaced more quickly or less quickly, corresponding tothe replacement rate that is needed.

Alternatively, the elements are on a conveyor belt mounted on a turningwheel, which belt continuously passes into and out of the reservoir asthe wheel turns.

Alternatively, each element undergoes a linear reciprocating motion,dipping into and out of the reservoir. Optionally, the changing weightof the desiccant when it becomes moisture laden (in the case of thedehumidifying section) or loses its moisture (in the case of theregenerating section) triggers the element to dip into the reservoir.

Optionally, the dipping motion of the elements, whether linear orrotary, intermittent or continuous, is driven by a motor. Optionally,the motor is powered by a battery or a solar cell. Alternatively, thedipping motion is driven by the same motor that drives an air intakefan, drawing outside air into the dehumidifier. Unless the dippingmotion is only intermittent, or the air intake fan is very big and slow,the air intake fan may turn faster than the rate of the dipping motionrequired for replacing the desiccant. Optionally, a set of gears is usedto reduce the speed of the dipping motion to an appropriate speed forreplacing the desiccant. Optionally, the same motor drives the elementsin the dehumidifying section and in the regenerating section.

It is important not to confuse this aspect of the invention with a wellknown prior art, in which a wheel is used to move desiccant (usuallysolid desiccant) from a dehumidifying section, where the desiccantabsorbs moisture from the air, to a regenerating section, where thedesiccant is heated and gives up its moisture, and back to thedehumidifying section. In the present invention, the elements do notmove desiccant between the dehumidifying section and the regeneratingsection, but between the reservoir and the air within the dehumidifyingsection or between the reservoir and the air within the regeneratingsection. In addition to this motion, moisture is transferred by othermeans from the reservoir associated with the dehumidifying section tothe reservoir associated with the regenerating section. Optionally thisis done by pumping, gravity, diffusion, any combination of these, or anyother means known to the art. For example, it is optionally done by acombination of gravity and diffusion, as described in unpublished PCTApplications PCT/IL01/00373 and PCT/IL01/00374, the disclosures of whichare incorporated herein by reference.

Using a wheel, belt, or similar mechanical system to circulate desiccantout of and into the reservoir has some advantages over the prior art ofspraying, dripping, or wicking the desiccant from the reservoir.Wicking, as described in unpublished PCT Application PCT/IL01/00374, isslower than the other methods, since the dehumidification rate orregenerating rate is limited by the speed at which water flows down thewick into the reservoir in the dehumidifying section, and up the wickfrom the reservoir in the regenerating section. Dripping requires somepower to lift the desiccant up to the point where it is dripped, andrequires special pumps to pump the (generally corrosive) desiccant.

With a wheel or belt, on the other hand, if the desiccant is absorbedinto an absorbent material using capillary action, then, in principle,no power is needed to move the desiccant into and out of the reservoirin the dehumidifying area, since the weight of the moisture-ladendesiccant traveling down into the reservoir is greater than the weightof the fresh desiccant being lifted out of the reservoir. If frictionand drag are kept low enough, the potential energy gained by loweringthe moisture from the air into the reservoir could be used to overcomethe friction and drag, and the wheel or belt could operate with noexternal power. Such a self-powered wheel or belt is not possible in theregenerating section. In general, in the dehumidifying section orregenerating section, a belt or wheel can be driven by a relatively lowpower motor, or, in the case of a wheel driven like a windmill, arelatively small amount of extra power needs to be put into the air flowby the intake fan.

Neither dripping nor spraying provides a simple feedback system forcontrolling the rate at which desiccant is circulated, although moreelaborate feedback systems involving sensors and controllers arepossible. With a wheel driven like a windmill by the incoming airstream, there is a natural relation between the rate of circulation ofdesiccant into and out of the reservoir, and the rate at which desiccantbecome saturated with moisture in the dehumidifying area, or free ofmoisture in the regenerating area, and needs to be replaced by desiccantfrom the reservoir.

A second aspect of some embodiments of the invention concerns a combineddehumidifying/air-conditioning system, in which water and air, at lessthan 100% humidity, are cooled off by allowing the water to evaporateinto said air, and the resulting cooled water and/or cooled but humidair is used to cool desiccant that is being used to absorb moisture inthe dehumidifier, by heat exchange. Without cooling, the desiccant wouldget hotter than the ambient air as it absorbed moisture from the air,due to the heat of vaporization of the moisture. Alternatively oradditionally, any other source of water, air, or another fluid, or anycombination of these, even at or above the ambient temperature, is usedto cool the desiccant. Alternatively or additionally, water and air arecooled off by letting the water evaporate into said air, and theresulting cooled water and/or cooled but humid air are used to cool warmdehumidified air, by heat exchange. Optionally, the air into which thewater is evaporated is also warm dehumidified air. Alternatively, theair into which the water is evaporated is ambient air, if the ambienthumidity is not too high, or a mixture of dehumidified air and ambientair.

The cooling that is accomplished in this way requires much less powerthan if a heat pump were used. If the water is evaporated into ambientair, then the cooling is essentially cost free, since it makes use ofthe internal energy associated with the fact that the ambient air hashumidity less than 100%. The power needed to overcome pipe losses andpump the cool water and/or air through the heat exchanger can be quitesmall, compared to the power that would be needed to cool the desiccantor the warm dehumidified air using a heat pump. If the water isevaporated into air that has been dehumidified, then some of theinternal energy comes, ultimately, from the heat that is used toregenerate the desiccant that did the dehumidifying. If the dehumidifieruses a source of waste heat to regenerate the desiccant, then thatenergy is essentially cost-free as well.

Although prior art systems using evaporation for cooling share thisfeature of low power requirements, they introduce into theair-conditioned environment air that has higher moisture content thanthe ambient air. In some embodiments of the invention, the moist cooledair is not released into the air-conditioned environment, but is onlyused in heat exchangers to cool other air directly (or indirectly bycooling desiccant), and then released into the ambient environment.Thus, the advantage of low power requirements can be obtained, withoutthe disadvantage of introducing moist air into the air-conditionedenvironment.

There is thus provided, in accordance with an embodiment of theinvention, an air-conditioning system for conditioning air by removingheat and moisture from the air and transferring it to the environment,comprising:

a dehumidifier that produces dehumidified air and utilizes a liquiddesiccant for drying;

at least one non-desiccant fluid at a temperature lower than thetemperature of the liquid desiccant; and

at least one heat exchanger in which the liquid desiccant is cooled bythe at least one fluid.

In a embodiment of the invention, at least one of the at least onefluids comprises water.

Alternatively or additionally, at least one of the at least one fluidscomprises air.

In an embodiment of the invention, there is at least one cooling chamberthrough which air flows, and which contains water which evaporates intosaid air, wherein the at least one fluid comprises one or both of airexiting at least one of the at least one cooling chambers and watercooled in at least one of the at least one cooling chambers.

Optionally, the water in at least one of the at least one coolingchambers is sprayed into the air in said cooling chamber.

Optionally, at least some of the air flowing through at least one of theat least one cooling chambers comprises at least some of thedehumidified air produced by the dehumidifier.

Alternatively or additionally, at least some of the air flowing throughat least one of the at least one cooling chambers comprises air that hasnot been dehumidified by the dehumidifier.

Optionally, at least one of the at least one heat exchangers is inthermal contact with at least one of the at least one cooling chambers.

Optionally, there is a desiccant pump which pumps the desiccant throughat least one of the at least one heat exchangers.

Alternatively there is a desiccant reservoir, the liquid desiccantutilized by the dehumidifier is contained at least part of the time inthe desiccant reservoir, and at least one of the at least one heatexchangers is in thermal contact with the desiccant reservoir.

There is further provided, in accordance with an embodiment of theinvention, an air-conditioning system for conditioning air by removingheat and moisture from the air and transferring it to the environment,comprising:

a dehumidifier which produces dehumidified air;

at least one cooling chamber through which air flows, and which containswater which evaporates into said air; and

at least one heat exchanger in which at least some of the dehumidifiedair is cooled by one or both of air exiting at least one of the at leastone cooling chambers or water cooled in at least one of the at least onecooling chambers.

In an embodiment of the invention, the dehumidifier utilizes a liquiddesiccant for drying, and the liquid desiccant is cooled in at least oneof the at least one heat exchangers by one or both of air exiting atleast one of the at least one cooling chambers or water cooled in atleast one of the at least one cooling chambers.

Optionally, the at least one heat exchangers comprise a first heatexchanger in which the liquid desiccant is cooled, and a second heatexchanger in which at least some of the dehumidified air is cooled.

Optionally, the at least one cooling chambers comprise a first coolingchamber and a second cooling chamber, wherein one or both of the airexiting from the first cooling chamber or the water cooled in the firstcooling chamber is used to cool the liquid desiccant, and one or both ofthe air exiting from the second cooling chamber or the water cooled inthe second cooling chamber is used to cool at least some of thedehumidified air.

Optionally, air exiting at least one of the at least one coolingchambers is used to cool the liquid desiccant.

Alternatively or additionally, water cooled in at least one of the atleast one cooling chambers is used to cool the liquid desiccant.

Optionally, there is a desiccant pump which pumps the desiccant throughat least one of the at least one heat exchangers.

Alternatively, there is a desiccant reservoir, the liquid desiccantutilized by the dehumidifier is contained at least part of the time inthe desiccant reservoir, and at least one of the at least one heatexchangers is in thermal contact with the desiccant reservoir.

Optionally, the water in at least one of the at least one coolingchambers is sprayed into the air in said cooling chamber.

Optionally, at least some of the air flowing through at least one of theat least one cooling chambers comprises at least some of thedehumidified air produced by the dehumidifier.

Alternatively or additionally, at least some of the air flowing throughat least one of the at least one cooling chambers comprises air that hasnot been dehumidified by the dehumidifier.

In an embodiment of the invention, the air exiting at least one of theat least one cooling chambers is used to cool the dehumidified air.

Alternatively or additionally, water cooled in at least one of the atleast one cooling chambers is used to cool the dehumidified air.

Optionally, at least one of the at least one heat exchangers is inthermal contact with at least one of the at least one cooling chambers.

There is further provided, in accordance with an embodiment of theinvention, a dehumidifier for removing moisture from air to be dried andtransferring it to environmental air, comprising:

liquid desiccant;

a dehumidifying section;

a dehumidifying section reservoir containing at least some of the liquiddesiccant; and

at least one dehumidifying section element;

wherein each dehumidifying section element moves from the dehumidifyingsection reservoir to the dehumidifying section, carrying some of thedesiccant from the dehumidifying section reservoir with it, whichdesiccant absorbs moisture from the air to be dried in the dehumidifyingsection, and the said dehumidifying section element then moves back tothe dehumidifying section reservoir, carrying the desiccant back to thedehumidifying section reservoir.

There is further provided, in accordance with an embodiment of theinvention, a dehumidifier for removing moisture from air to be dried andtransferring it to environmental air, comprising:

liquid desiccant;

a dehumidifying section where the liquid desiccant removes moisture fromthe air;

a regenerating section;

a regenerating section reservoir containing at least some of the liquiddesiccant; and

at least one regenerating section element;

wherein each regenerating section element moves from the regeneratingsection reservoir to the regenerating section, carrying some of thedesiccant from the regenerating section reservoir with it, whichdesiccant gives up moisture to the environmental air in the regeneratingsection, and the said regenerating section element then moves back tothe regenerating section reservoir, carrying the desiccant back to theregenerating section reservoir.

Optionally, at least one dehumidifying section elements movescontinuously.

Alternatively or additionally, at least one of the at least onedehumidifying section elements moves intermittently.

In an embodiment of the invention, the rate at which the desiccantcarried by at least one of the at least one dehumidifying sectionelements is replaced by desiccant from the dehumidifying sectionreservoir depends on the rate at which the desiccant carried by saiddehumidifying section element absorbs moisture from the air to be dried.

Optionally, there is a sensor which senses the amount of moistureabsorbed by the desiccant in at least one of the at least onedehumidifying section elements, and a controller which causes saiddehumidifying section element to move or to move faster when theabsorbed moisture exceeds a given level.

Optionally, the air to be dried moves through the dehumidifying section,and said motion of the air to be dried causes or contributes to causingat least one of the at least one dehumidifying section elements to move.

Alternatively or additionally, there is a motor operative to move atleast one of the at least one dehumidifying section elements.

In an embodiment of the invention, there is at least one wheel whichcomprises at least one of the at least one dehumidifying sectionelements, and a rotating of the wheel comprises the moving of at leastone of the at least one dehumidifying section elements that said wheelcomprises.

Alternatively or additionally, there is at least one conveyor belt whichcomprises at least one of the at least one dehumidifying sectionelements, and a conveying of the belt comprises the moving of at leastone of the at least one dehumidifying section elements that said beltcomprises.

Optionally, at least one of the at least one dehumidifying sectionelements comprises absorbent material.

Alternatively or additionally, the desiccant adheres to at least one ofthe at least one dehumidifying section elements because of viscosity orsurface tension.

Alternatively or additionally, at least one of the at least onedehumidifying section elements comprises at least one hollow space, andthe desiccant remains in said space for at least a portion of themovement of the element.

Optionally, there is a dehumidifying section desiccant remover whichremoves desiccant from at least one of the at least one dehumidifyingsection elements, after said desiccant has absorbed moisture from theair to be dried in the dehumidifying section, and before said elementcarries desiccant from the dehumidifying section reservoir to thedehumidifying section for a further drying cycle.

Optionally, the removal of desiccant from at least one of the at leastone dehumidifying section elements is done by any one or a combinationof squeezing, scraping, wiping, and siphoning the said dehumidifyingsection element.

Alternatively or additionally, the removal of desiccant from at leastone of the at least one dehumidifying section elements is done bytipping the said dehumidifying section element.

Optionally, at least one of the at least one regenerating sectionelements moves continuously.

Alternatively or additionally, at least one of the at least oneregenerating section elements moves intermittently.

In an embodiment of the invention, the rate at which the desiccantcarried by at least one of the at least one regenerating sectionelements is replaced by desiccant from the regenerating sectionreservoir depends on the rate at which the desiccant carried by saidregenerating section element gives up moisture to the environmental airin the regenerating section.

Optionally, there is a sensor which senses the amount of moistureabsorbed by the desiccant in at least one of the at least oneregenerating section elements, and a controller which causes saidregenerating section element to move or to move faster when the absorbedmoisture falls below a given level.

Optionally, the environmental air moves through the regeneratingsection, and said motion of the environmental air causes or contributesto causing at least one of the at least one regenerating sectionelements to move.

Additionally or alternatively, there is a motor operative to move atleast one of the at least one regenerating section elements.

Optionally, there is at least one wheel which comprises at least one ofthe at least one regenerating section elements, and a rotating of thewheel comprises the moving of at least one of the at least oneregenerating section elements that said wheel comprises.

Alternatively or additionally, there is at least one conveyor belt whichcomprises at least one of the at least one regenerating sectionelements, and a conveying of the belt comprises the moving of at leastone of the at least one regenerating section elements that said beltcomprises.

Optionally, at least one of the at least one regenerating sectionelements comprises absorbent material.

Alternatively or additionally, the desiccant adheres to at least one ofthe at least one regenerating section elements because of viscosityand/or surface tension.

Alternatively or additionally, at least one of the at least oneregenerating section elements comprises at least one hollow space, andwherein the desiccant remains in said space for at least a portion ofthe movement of the element.

In an embodiment of the invention, there is a regenerating sectiondesiccant remover which removes desiccant from at least one of the atleast one regenerating section elements, after said desiccant has givenup moisture to the environmental air in the regenerating section, andbefore said element carries desiccant from the regenerating sectionreservoir to the regenerating section for a further regenerating cycle.

Optionally, the removal of desiccant from at least one of the at leastone regenerating section elements is done by any one or a combination ofsqueezing, scraping, wiping, and siphoning the said regenerating sectionelement.

Alternatively or additionally, the removal of desiccant from at leastone of the at least one regenerating section elements is done by tippingthe said regenerating section element.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are described in the followingsections with reference to the drawings. The drawings are generally notto scale and the same or similar reference numbers are used for the sameor related features on different drawings.

FIGS. 1 and 4 schematically show combined dehumidifying/air-conditioningsystems, according to some embodiments of the invention;

FIG. 2 is a plot of temperature vs. moisture content for air at sealevel, showing the paths taken by air at different stages of the coolingand dehumidifying process in the apparatus shown in FIG. 1; and

FIG. 3A and FIG. 3B show two different side views, and FIG. 3C shows atop view, of a dehumidifier, according to an embodiment of theinvention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 schematically shows a combined dehumidifying/air-conditioningsystem, according to an exemplary embodiment of the invention. Warm andhumid air 10 is drawn by an intake fan 12 into a dehumidifying chamber14 which is associated with a reservoir 16 filled with liquid desiccant.Optionally, the dehumidifier uses a rotating wheel or belt or similarmechanism (not shown in FIG. 1), to circulate desiccant out of and intoreservoir 16, as will be described in detail in FIG. 3, exposing thedesiccant to the air and allowing the desiccant to absorb moisture fromthe air. Alternatively, the dehumidifier uses a prior art method ofexposing the desiccant to the air, such as spraying, dripping, orwicking the desiccant. FIG. 1 shows a pump 17, which draws the desiccantout of reservoir 16, and drips or sprays it through the air. Aregenerating chamber 42, adjacent to the dehumidifying chamber, has itsown reservoir 46 of liquid desiccant, and its own pump 18, which drawsdesiccant out of reservoir 46 and drips or sprays it through the air inregenerating chamber 42. Alternatively, the regenerating chamber usesanother method of exposing the desiccant to the air, for examplewicking, or using a rotating wheel, belt or similar mechanism asdescribed in FIG. 3. The regenerating chamber has its own intake fan 19which draws ambient air into the regenerating chamber. Alternatively, asingle fan, and an intake duct that splits into two parts, is used todraw ambient air into both the dehumidifying chamber and theregenerating chamber.

A heater 50 heats the air flowing into regenerating chamber 42, loweringthe humidity of the air. Optionally, the heater is a heat exchanger,which uses a source of waste heat, generally available in largebuildings. Alternatively or additionally, the heater is an electricheater, or any other kind of heater known to the art. Optionally, heater50, or another heater, heats the desiccant in reservoir 46 or elsewherein regenerating chamber 42, in addition to or instead of heating the airflowing into regenerating chamber 42. Sufficiently heating the desiccantin regenerating chamber 42 and/or lowering the humidity of the air inregenerating chamber 42 will make the desiccant give up moisture to theair, instead of absorbing moisture from the air as occurs indehumidifying chamber 14. The moist air in regenerating chamber 42 isreturned to the outside environment through an exit duct 21.

In an embodiment of the invention, there is at least one small hole 48between reservoir 16 and reservoir 46. As described in unpublished PCTApplications PCT/IL01/00373 and PCT/IL01/00374, a combination of gravityand diffusion causes moisture to move from reservoir 16 through hole 48to reservoir 46, without the need to actively move desiccant between thereservoirs. As the desiccant in the dehumidifying section absorbs waterfrom the air, the volume of desiccant in reservoir 16 increases. At thesame time, as the desiccant in the regenerating section gives upmoisture to the air, the volume of desiccant in reservoir 46 decreases.Gravity causes moisture laden desiccant from reservoir 16 to flowthrough hole 48 into reservoir 46, to keep the two reservoirs at nearlythe same level. In equilibrium, there is a net flow of water fromreservoir 16 to reservoir 46, and there is a counter flow of desiccantions diffusing through hole 48 from reservoir 46 to reservoir 16, tobalance the gravity assisted flow of desiccant ions going the otherdirection, resulting in a net zero flow of desiccant ions. This methodof transferring moisture and circulating the desiccant between the tworeservoirs avoids unnecessary transfer of heat from reservoir 46 toreservoir 16. Alternatively or additionally, desiccant is pumped fromreservoir 16 to reservoir 46 and back, in order to remove moisture fromit, as in the art prior to PCT/IL01/00373. Such pumping is optionallyused, for example, in order to increase the rate at which moisture flowsfrom reservoir 16 to reservoir 46, in order to improve the effectivenessof the dehumidification, even at the cost of decreasing theeffectiveness or efficiency of the cooling. Optionally, desiccant ispumped in one direction, and made to flow in the other direction bygravity.

A heat exchanger 20 is located in reservoir 16, and the desiccant inreservoir 16 is cooled by water that is pumped through the heatexchanger from a cooling chamber 22, by a pump 24. Alternatively, heatexchanger 20 is located in cooling chamber 22 and the desiccant ispumped, optionally by pump 17, from reservoir 16 through the heatexchanger and back to reservoir 16. Alternatively, heat exchanger 20 islocated outside both reservoir 16 and cooling chamber 22, and both waterfrom cooling chamber 22 and desiccant from reservoir 16 are pumpedthrough heat exchanger 20 and back. For example, as shown in FIG. 4,pumps 51 and 53 pump the desiccant trough heat exchanger 20 and back.

In cooling chamber 22, the water is cooled below the ambient airtemperature by allowing the water to evaporate into ambient air drawninto and through the cooling chamber by fan 26. Optionally, the water issprayed through the air in cooling chamber 22 to facilitate evaporation,optionally using pump 24 as shown in FIG. 1, or any other means known tothe art is used to facilitate evaporation. The air is also cooled bythis process, and alternatively the cooled air is used, instead of or inaddition to the cooled water, to cool the desiccant in heat exchanger20. This cooling of the desiccant in heat exchanger 20 prevents thedesiccant from heating up as much as it would if the dehumidification indehumidifying chamber 14 occurred at constant enthalpy, and optionallythe equilibrium temperature of the desiccant is even below the ambienttemperature of the air. The cooled desiccant in turn keeps thedehumidified air leaving chamber 14 at a lower temperature than if itwould have if it were dehumidified at constant enthalpy, and optionallyeven cools it below the ambient temperature.

Instead of or in addition to using water and/or air cooled in coolingchamber 22 to cool the desiccant, heat exchanger 20 optionally uses anyother source of water and/or air, or any other fluid, to cool thedesiccant, even water or air that is at or above the ambienttemperature. As long as the water or air used in heat exchanger 20 has alower temperature than the temperature that the desiccant would reach ifit absorbed the moisture at constant enthalpy, heat exchanger 20 willstill cool the desiccant.

In some embodiments of the invention, the dehumidified air flows out ofchamber 14 through a duct 28, which splits into two parts. Part of theair flows through a duct 29, and part of the air flows through a duct 30into a second cooling chamber 32, where water evaporates into it,optionally facilitated by spraying the water through said air, or by anyother means known to the art. Because the air entering cooling chamber32 has lower humidity than the ambient air entering cooling chamber 22,and does not differ greatly in temperature from the ambient air, the airand water in chamber 32 are cooled by the evaporation to an even lowertemperature than the air and water in chamber 22. Some or all of thecooled water from chamber 32 is used to cool the air flowing throughduct 29, in a heat exchanger 34. Alternatively or additionally, thecooled air from chamber 32 is used in heat exchanger 34 to cool the airflowing through duct 29. Optionally, heat exchanger 34 is located insidecooling chamber 32 and duct 29 passes through cooling chamber 32.Alternatively, heat exchanger 34 is located outside cooling chamber 32,adjacent to duct 29, and water and/or air from cooling chamber 32 ispumped or made to flow into heat exchanger 34. The air from duct 29 doesnot mix with the moist air or water from chamber 32, and is only cooledby it, so air from duct 29 remains dry after passing through heatexchanger 34. This dry, cool air is used for output air 36 from the airconditioner. Air 38 that has passed through chamber 32 is not used asoutput air from the air conditioner, because it has high humidity, so itis vented to the outside.

Optionally, dehumidified air from duct 28, or a mixture of dehumidifiedair and ambient air, is used in cooling chamber 22, instead of ambientair. Optionally, ambient air, or a mixture of dehumidified air andambient air, is used cooling chamber 32, instead of dehumidified air.Optionally, instead of two cooling chambers 22 and 32, there is only onecooling chamber, and it used both for cooling desiccant in thedehumidifying section, and for cooling dehumidified air exiting thedehumidifying section through duct 28.

FIG. 2 is a chart showing curves of constant relative humidity andconstant enthalpy, as a function of temperature and moisture content,for air at sea level. If the ambient air is at 35 degrees C. and 70%humidity, then, if the water in chamber 22 is allowed to evaporate intothe ambient air at constant enthalpy until it reaches 100% humidity(path 101 in FIG. 2), its temperature will fall to 30 degrees C. This isthe lowest temperature that the water in chamber 22 can reach byconstantly evaporating it into ambient air, and by thermally insulatingit from the outside environment. If the ambient air enteringdehumidifying chamber 14 were allowed reach a humidity of 40% atconstant enthalpy (path 102), it would have a temperature of 43 degreesC., and (ignoring the additional heating of the desiccant in theregenerator chamber) the desiccant would reach an equilibriumtemperature of 43 degrees C. if it were thermally insulated from theoutside. By using the water from chamber 22 to cool the desiccant as itis reducing the humidity of the air from 70% to 40%, the equilibriumtemperature of the desiccant can be brought to a point somewhere between43 degrees and 30 degrees, and the air flowing out of chamber 14 throughduct 28 can be brought to the same temperature. For example (path 103),this temperature can be 33 degrees.

The air flowing through duct 30, which starts at 33 degrees and 40%humidity, will reach 22 degrees if water is evaporated into it atconstant enthalpy until it reaches 100% humidity (path 104). So the airflowing through chamber 32, and the water in chamber 32, could reach atemperature as low as 22 degrees, if chamber 32 is thermally insulatedfrom the ambient environment. The air flowing through duct 29, afterexchanging heat with the air or water from chamber 32, will reach atemperature somewhere between 33 degrees (the initial temperature of theair from duct 29 as it flows into the heat exchanger) and 22 degrees(the temperature of the water or air coming from chamber 32). Forexample, it could end up at a temperature of 25 degrees (path 105). Itsmoisture content will remain the same as it was before entering heatexchanger 34, and its final humidity will be 64%.

FIGS. 3A, 3B and 3C show a dehumidifier, according to an embodiment ofthe invention. FIG. 3A is a view from one side, FIG. 3B is a view fromanother side, looking from the left in FIG. 3A, and FIG. 3C is a viewfrom the top. Optionally, the dehumidifier shown in FIGS. 3A-3C is usedas the dehumidifying component of a combineddehumidifying/air-conditioning system, such as that shown in FIG. 1.Alternatively, the dehumidifier shown in FIGS. 3A-3C is used as a standalone dehumidifier.

In FIG. 3A, ambient air 10 is drawn by an intake fan 12 into adehumidifying chamber 14, with a reservoir 16 of liquid desiccant at thebottom of the chamber. A windmill or a set of windmills 40 is mountedinside the chamber, so that the flowing air will cause them to turn.(each windmill shown in FIG. 3A optionally represents a row of severalwindmills, one behind the other on a common shaft, as may be seen inFIGS. 3B and 3C.) Alternatively or additionally, a motor supplies powerto turn the windmills, possibly the same motor that drives the intakefan. Each windmill has several blades, covered with an absorbentmaterial, for example felt or sponge. As the windmill turns, the bladessuccessively dip into the reservoir, and the covering absorbs desiccant.The blade then goes through the air, where the desiccant absorbsmoisture. When the blade returns to the reservoir, the moisture ladendesiccant, or the moisture in the desiccant, diffuses into thereservoir, and the absorbent material contains desiccant with lessmoisture when the blade again surfaces and travels through the air.Optionally, the exchange of moisture laden desiccant for fresh desiccantmay be aided by having the blades pass through a squeegee like device,or a device that presses against the blades on one side, before enteringthe reservoir, or while in the reservoir, although this may increase theforce required to turn the windmill.

Eventually, the desiccant in the reservoir will become saturated withmoisture unless moisture is removed. To prevent this from happening,moisture is removed from the desiccant in a regenerator. FIG. 3B shows aside cross sectional view of the dehumidifier, as seen from thedirection of the air flow. Dehumidifying chamber 14, also seen in FIG.3A, is on the left in FIG. 3B, and a regenerating chamber 42, not shownin FIG. 3A, is on the right in FIG. 3B. A wall 43 separatesdehumidifying chamber 14 from regenerating chamber 42. Sets of windmills44 are located in the regenerating chamber, similar to the windmills 40in the dehumidifying chamber. A reservoir 46, filled with liquiddesiccant, is located at the bottom of regenerating chamber 42, similarto reservoir 16 in dehumidifying chamber 14. Optionally wall 43,especially the part of wall 43 separating reservoir 16 from reservoir46, is well insulated thermally. An intake duct with an intake fan 19,not shown in FIG. 3A or 3B but shown in FIG. 3C, located at one end ofthe regenerating chamber, for example next to intake fan 12, drawsambient air into regenerating chamber 42, and blows it past windmills44.

At least one small hole 48 optionally connects dehumidifier reservoir 16and regenerator reservoir 46, as described previously in the descriptionof FIG. 1. Optionally there are several holes, lined up in the directionof the air flow, and/or one above the other. Alternatively oradditionally, desiccant is pumped from dehumidifier reservoir 16 toregenerator reservoir 46 and pumped back, pumped in one direction andcaused to flow in the other direction by gravity, or caused to circulatebetween reservoir 16 and reservoir 46 by any other method known to theart. Optionally, reservoir 16 and reservoir 46 are connected by one ormore pipes instead of or in addition to one or more holes, andoptionally there are not adjacent to each other.

Optionally, a heater 50 heats the desiccant in reservoir 46. Optionally,heater 50 is a heat exchanger, supplied with waste heat from outsidesource. Alternatively or additionally, heater 50 is an electric heater,or any other kind of heater known to the art. Heater 50 heats thedesiccant in reservoir 46 to a high enough temperature so that it givesoff moisture, rather than absorbing moisture from the air, at theambient moisture content of the air. Optionally, heater 50, or anotherheater, heats the air flowing through regenerating chamber 42, as shownin FIG. 1, in addition to or instead of heating the desiccant inreservoir 46. Heating the air will lower its relative humidity, andcause the desiccant give up moisture to the air at a lower desiccanttemperature than would be necessary if the air were not heated. Heatingthe air will also cause the desiccant to give up moisture to the airmore rapidly, at the same desiccant temperature. The air flowing throughregenerating chamber 42 exits the chamber through a duct 52, shown onlyin FIG. 3C, and returns to the ambient environment. Optionally, duct 52is at the side of chamber 42 opposite to intake duct and fan 19, and theair flowing out of duct 52 is directed into the ambient environment insuch a way as to keep it away from either the intake duct of thedehumidifying chamber or the intake duct of the regenerating chamber.

Alternatively, instead of or in addition to using a heat exchanger orheater to heat the desiccant and/or air in regenerating chamber 42, aheat pump is used to transfer heat from dehumidifying chamber 14 toregenerating chamber 42. Other details are optionally incorporated thatare described in the description of FIG. 1, or are known to the art.See, for example, the prior art references referred to above.

Other embodiments of the invention employ means other than windmills tocirculate the desiccant out of one or both reservoirs, into the air, andback again. Some of these means are described above in the “Summary ofInvention.” Some of these means involve using a motor to intermittentlyturn a wheel or belt with desiccant absorbed in it, and with part of thewheel or belt immersed in the reservoir, and part of the wheel or beltexposed to the air flow. Optionally, the motor is automatically turnedon when the wheel or belt reaches a certain weight, as moisture isabsorbed from the air in the dehumidifying chamber, or as moisture isgiven off into the air in the regenerating chamber. Alternatively,instead of relying on the changing weight of the desiccant, a chemicalsensor, mounted in the absorbent material, detects the moisture, andturns on the motor when the moisture reaches a certain level.Alternatively, the motor turns on at intervals that are calculated by acontroller as the time needed to saturate the desiccant in the absorbentmaterial, according to a sensed humidity and temperature of the incomingair. Alternatively, the motor does not make use of feedback at all, butturns on at fixed intervals, independent of the humidity and temperatureof the incoming air.

The words “comprise”, “have” and “include” and their conjugates as usedherein mean “include but are not necessarily limited to.” While theinvention has been described with reference to certain exemplaryembodiments, various modifications will be readily apparent to and maybe readily accomplished by persons skilled in the art without departingfrom the spirit and scope of the above teachings.

1. A dehumidifier for removing moisture from air to be dried andtransferring it to environmental air, comprising: liquid desiccant; adehumidifying section; a dehumidifying section reservoir of having saidat least two reservoirs containing at least some of the liquiddesiccant; and at least one dehumidifying section element; wherein eachdehumidifying section element moves from the dehumidifying sectionreservoir to the dehumidifying section, carrying some of the desiccantfrom the dehumidifying section reservoir with it, which desiccantabsorbs moisture from the air to be dried in the dehumidifying section,and the dehumidifying section element then moves back to thedehumidifying section reservoir, carrying the desiccant back to thedehumidifying section reservoir, and wherein the air to be dried movesthrough the dehumidifying section, and said motion of the air to bedried causes or contributes to causing at least one of the at least onedehumidifying section elements to move.
 2. An air-conditioning systemfor conditioning air by removing heat and moisture from the air andtransferring it to the environment, comprising: the dehumidifieraccording to claim 1; a cooling tower that provides at least onenon-desiccant fluid at a temperature lower than the temperature of theliquid desiccant in one of the reservoirs; and at least one heatexchanger situated in the one reservoir via which the liquid desiccantin the one reservoir is cooled by the at least one fluid.
 3. Theair-conditioning system according to claim 2, wherein said cooling towercomprises at least one cooling chamber through which air flows, andwhich contains water which evaporates into said air, wherein the atleast one fluid comprises one or both of air exiting at least one of theat least one cooling chambers and water cooled in at least one of the atleast one cooling chambers.
 4. The air-conditioning system according toclaim 3, wherein the water in at least one of the at least one coolingchambers is sprayed into the air in said cooling chamber.
 5. Theair-conditioning system according to claim 3, wherein at least some ofthe air flowing through at least one of the at least one coolingchambers comprises at least some of the dehumidified air produced by thedehumidifier.
 6. The air-conditioning system according to claim 3,wherein at least some of the air flowing through at least one of the atleast one cooling chambers comprises air that has not been dehumidifiedby the dehumidifier.
 7. The air-conditioning system according to claim3, wherein at least one of the at least one heat exchangers is inthermal contact with at least one of the at least one cooling chambers.8. The air-conditioning system according to claim 3, and including adesiccant pump which pumps the desiccant through at least one of the atleast one heat exchangers.
 9. The air-conditioning system according toclaim 3, and including a desiccant reservoir, wherein the liquiddesiccant utilized by the dehumidifier is contained at least part of thetime in the desiccant reservoir, and at least one of the at least oneheat exchangers is in thermal contact with the desiccant reservoir. 10.An air-conditioning system for conditioning air by removing heat andmoisture from the air and transferring it to the environment,comprising: the dehumidifier according to claim 1; and a regenerator,comprising: a regenerating section; a regenerating section reservoir ofsaid at least two reservoirs containing at least some of the liquiddesiccant; and at least one regenerating section element; wherein eachregenerating section element moves from the regenerating sectionreservoir to the regenerating section, carrying some of the desiccantfrom the regenerating section reservoir with it, which desiccant givesup moisture to the environmental air in the regenerating section, andthe said regenerating section element then moves back to theregenerating section reservoir, carrying the desiccant back to theregenerating section reservoir.
 11. The system according to claim 10,wherein at least one of the at least one dehumidifying section elementsmoves continuously.
 12. The system according to claim 10, wherein atleast one of the at least one dehumidifying section elements movesintermittently.
 13. The system according to claim 10, wherein the rateat which the desiccant carried by at least one of the at least onedehumidifying section elements is replaced by desiccant from thedehumidifying section reservoir depends on the rate at which thedesiccant carried by said dehumidifying section element absorbs moisturefrom the air to be dried.
 14. The system according to claim 10, whereinair moves through the dehumidifying or regenerating section, and saidmotion of the air to be dried causes or contributes to causing at leastone of the at least one dehumidifying or regenerating section elementsto move.
 15. The system according to claim 14, and including at leastone wheel which comprises at least one of the at least one dehumidifyingor regenerating section elements, wherein a rotating of the wheelcomprises the moving of at least one of the at least one dehumidifyingor regenerating section elements that said wheel comprises.
 16. Thesystem according to claim 15, wherein at least one of the at least onedehumidifying or regenerating section elements comprises absorbentmaterial.
 17. The system according to claim 15, wherein the desiccantadheres to at least one of the at least one dehumidifying orregenerating section elements because of viscosity or surface tension.18. The system according claim 15, wherein at least one of the at leastone dehumidifying or regenerating section elements comprises at leastone hollow space, and wherein the desiccant remains in said space for atleast a portion of the movement of the element.
 19. The system accordingto claim 3 the at least one fluid comprises air exiting at least one ofthe at least one cooling chambers.
 20. The system according to claim 3wherein the at least one fluid comprises both of air exiting at leastone of the at least one cooling chambers and water cooled in at leastone of the at least one cooling chambers.
 21. The air-conditioningsystem according to claim 20, wherein at least some of the air flowingthrough at least one of the at least one cooling chambers comprises atleast some of the dehumidified air produced by the dehumidifier.
 22. Theair-conditioning system according to claim 20, wherein at least some ofthe air flowing through at least one of the at least one coolingchambers comprises air that has not been dehumidified by thedehumidifier.
 23. The air-conditioning system according to claim 20,wherein at least one of the at least one heat exchangers is in thermalcontact with at least one of the at least one cooling chambers.
 24. Theair-conditioning system according to claim 20, and including a desiccantpump which pumps the desiccant through at least one of the at least oneheat exchangers.
 25. The air-conditioning system according to claim 2,wherein said cooling tower comprises at least one cooling chamberthrough which air flows, and which contains water which evaporates intosaid air, wherein the at least one fluid comprises one or both of airexiting at least one of the at least one cooling chambers and watercooled in at least one of the at least one cooling chambers, wherein atleast some of the air flowing through at least one of the at least onecooling chambers comprises at least some of the dehumidified airproduced by the dehumidifier.
 26. The air-conditioning system accordingto claim 25, wherein the water in at least one of the at least onecooling chambers is sprayed into the air in said cooling chamber. 27.The air-conditioning system according to claim 25, wherein at least oneof the at least one heat exchangers is in thermal contact with at leastone of the at least one cooling chambers.
 28. The air-conditioningsystem according to claim 25, and including a desiccant pump which pumpsthe desiccant through at least one of the at least one heat exchangers.29. The air-conditioning system according to claim 25, and including adesiccant reservoir, wherein the liquid desiccant utilized by thedehumidifier is contained at least part of the time in the desiccantreservoir, and at least one of the at least one heat exchangers is indirect thermal contact with the desiccant reservoir.
 30. A regeneratorfor removing moisture from a desiccant solution and transferring it toenvironmental air, comprising: liquid desiccant; a regenerating section;a regenerating section reservoir having at least two reservoirscontaining at least some of the liquid desiccant; and at least oneregenerating section element; wherein each regenerating section elementmoves from the regenerating section reservoir to the regeneratingsection, carrying some of the desiccant from the regenerating sectionreservoir with it, which desiccant gives up moisture to theenvironmental air in the regenerating section, and the said regeneratingsection element then moves back to the regenerating section reservoir,carrying the desiccant back to the regenerating section reservoir, andwherein air moves through the regenerating section and said motion ofthe air causes or contributes to causing at least one of the at leastone regenerating section elements to move.